Tension leverage for rope-drive elevators.



D. L. LINDQUIST. TENSION LEVERAGE FOR ROPE DRIVE ELEVATORS.

APPLICATION FILED MAY 7, 1908.

Patented Dec. 12, 1911.

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UNTTED s'raras arser ormon.

DAVID L. LINDQUIST, OF YONKERS, NEW YORK, ASSIGNOR T0 OTIS ELEVATOR COM-PANY, OF JERSEY CITY, NEW JERSEY, A CORPORATION OF NEW JERSEY.

TENSION LEVERAGE FOR ROPE-DRIVE ELEVATORS.

Specification of Letters Patent.

Application filed May 7, 1908.

To all whom it may concern:

Be it known that I, DAVID L. LINDQUIST, a subject of the King of Sweden,residing at Yonkers, in the county of Westchester and State of New York,have invented a new and useful Improvement in Tension Leverage forRope-Drive Elevators, of which the following is a specification.

My invention relates to improvements in traction or rope drive elevatorapparatus, and one of its objects is the provision of novel means forvarying the traction on the driving cables as the load on the carvaries.

Other objects of my invention will appear hereinafter, the novelcombinations of elements being set forth in the claims hereunto annexed.

In the accompanying drawing which illustrates an elevator embodying myinvention, Figure 1 is an elevation view of the elevator; Fig. 2 is aside elevation of the motor;

Fig. 3 is a sectional plan View taken substantially on the line a-a; ofFig. 1., and showing a floating lever and means for adjustablyconnecting the cables thereto; Fig. 4: is a sectional view of thefloating lever and associated parts.

M designates an electric motor arranged to drive a grooved tractionsheave S which is preferably mounted directly upon the motor shaft 10.The driving cables 11 are in frictional engagement with the tractionsheave S and are connected at one end to a suspended beam 12 by aneye-bolt or eyebolts 13, or other fastening means. The other ends areconnected to a counterbalance weight W. Other cables 14 are connected tothis counterbalance weight W and pass up over a pulley 15 which issupported by suitable bearings 16 mounted upon a stationary beam 17. Thecables 14 are also connected to the suspended beam 12 by eye-bolts 18. Aweight W is suspended by cables 19 which pass over a stationary pulley20 and are connected to the suspended beam 12 near one end thereof byeye-bolts 21.

C designates an elevator car which is adapted to travel on the usualguide rails 22, 22, and is suspended near the opposite end of the beam12 by the eye-bolt 23. The

beam 12 is provided with slots 21, 18 and 23, to provide for theadjustment of the fastenings 21, 18 and 23, respectively.

The movement of the elevator car 0 is controlled from within the same bymeans of a manually operated switch 24: which is arranged to eifect theoperation of a controlling device 25 wherein a pivoted arm 26 is adaptedto electrically engage a series of contacts 27, and thus effect thestarting, stopping, and reversing of the motor M in a well known way.

28 designates a source of electrical energy, such as a dynamo or othergenerator of electricity. Any other desired form of motor and system ofcontrol may be used in connection with my invention.

The suspended beam 12 is in effect a floating lever and is subjected tovarious forces acting in difierent directions at different locationsthereon. At the point of suspension 23 the car and its load are exertinga downward pull. At the point 18 the counterbalance weight W is exertingan upward pull. The point 13 is held stationary by the driving cables 11when the motor is at rest, while at 21 there is an upward pull due tothe weight W.

Assuming the motor M to be at rest and the various parts in the relativepositions shown in the drawing, the suspended beam 12 is held in a stateof equilibrium. Assuming, further, the point 18 as a fulcrum, it is seenthat the tension on the driving cables 11 lying on the right-hand sideof the traction sheave S is due to the weight of the car and its loadand the weight W, each producing an upward pull upon the cables 11 atthe point 13. This upward pull at 13, however, is in excess of thecombined weights of the car and its load and the weight W, owing to theleverage obtained by these weights operating about the point 18 as afulcrum.

In order to illustrate the effect of the 9 various weights on thetension of the driving cables, let the following conditions be assumed:the weight of the empty car 2,000 lbs., the weight of the counterbalanceweight W 1,500 lbs, and the weight of the auxiliary weight W 500 lbs.;the horizontal distances between the suspension points 21-13, 13-18, and1823, 1 foot, 1 foot, and 2 feet, respectively. The weight of the lever12 is here neglected, although it may also be relied on to assist thecar and load in bending the driving cables onto the driving sheave. Now,considering the point 18 as a fulcrum, the tension on the cables 11 atthe point 13 due to the weight of the car alone is 1,000

lbs, or double that of the car itself, since the length of the lever armbetween the points 18 and 23 is double that of the arm between thepoints 18 and 13. In a similar manner the tension on the cables 11 atthis same point 13 due to the weight W, is double that of the weight ofWV, or 1,000 lbs. The total tension upon the cables 11 at the point 13or upon the right-hand side of the traction sheave S is therefore 4,000lbs.+1,000 lbs, or 5,000 lbs. It is evident that the tension upon thecables 14 at the point 18 is equal to the weight of the car added to thetension upon the cables 11 at the point 13, less the weight WV, whichexpressed in figures will be 2,000 lbs.+5.-000 lbs.500 lbs.:6,500 lbs.The tension upon the driving cables 11 adjacent to. the lefthand side ofthe traction sheave S equals the tension upon the cables 14 at the point18, less the weight of the counterbalance weight W, or 6,500 lbs.-1,500lbs.:5,000 lbs. Thus it is seen that in the example given the tension ofthe driving cables 11 upon either side of the traction sheave S is equalto 5,000 lbs., making a total upward pull upon this sheave of 10,000lbs. which is considerably in excess of the combined weights of the car,counterbalance and auxiliary weight IV, their combined Weight being only4,000 lbs. It should also be noted that both leads are put under thesame strain so that there is no tendency for the cable 11 to slip on thedriving sheave. If a load of 500 lbs. is now added to the weight of thecar it is readily ascertained by proceeding as in the above example thatthe tension on the driving cables 11 on the right-hand side of thetraction sheave S is 6,000 lbs. and on the left-hand side 6,500 lbs, thetotal tension or upward pull upon the traction sheave being therefore12.500 lbs. -By comparing this result with that found in the case of anempty car, viz,

10,000 lbs, it becomes apparent that the increase in total tension uponthe traction sheave caused by the load of 500 lbs. in the car, is thedifference between 12,500 lbs. and 10,000 lbs., or 2,500 lbs. The ratio.between the total tension (12,500 lbs.) on the traction sheave and thecar and load 2,500 lbs.) is therefore 5 to 1, and this ratio is true inevery instance where the load in the car is the only quantity varyingfrom the conditions specified in the above examples. If the car isempty, the ratio is 10,000 to 2,000 or 5 to 1, also.

In order to increase the ratio between the load on the car and the totaltension on the traction sheave, the point of suspension 18 may be placedcloser to the point 13, there by increasing the leverage of both the carand auxiliary weight W. Utilizing the same weights as before in the caseof an empty car and moving the point 18 six inches nearer the point 13,it is found that the tension on either side of the traction drivingsheave S is 11,500 lbs. making a total tension of twice 11,500 lbs. or23,000 lbs. By now adding a load of 500 lbs. to the car, it will befound that the tension on the left side of the traction sheave is 14,500lbs. and on the right side 14,000 lbs., making a total tension of 28,500lbs. The corresponding total tension in the case of an empty car was23,000 lbs., making a difference of 5,500 lbs. due to the load of 500lbs. placed in the car. Where the ratio before was 5 to 1, the ratiounder the new conditions is 11 to 1, the difference between the tworatios being caused by merely moving the suspension point 18 a distanceof six inches. The important feature of the invention, however, is thatthe difference in tension in leads extending from the driving sheave ascompared with the total tension in said leads varies but little withincrease of load. Under certain conditions of practice, if thisdiiference should exceed 50% of the tension on the lead having thelesser tension there would be slipping, but it will be seen that even ifthe load were increased to 8,000 lbs, the tension in the left-hand leadwould be 29,000 lbs. and in the righthand lead 21,000 lbs., thedifference being 8,000 lbs. or about 38.1% of 21,000 lbs. the

tension on the right hand lead. Therefore, starting with a car weighing2,000 lbs, the difference in the tensions in the leads ex tending fromthe driving sheave would never be sufiiciently great in practice toefiect any slipping of the driving ropes on the driving sheave.

From the foregoing examples it is readily seen that by varying theposition of the cable fastening 18, or by varying any of the othersuspension points, any desired ratio between the tension on the drivingcables and the load on the car may be obtained.

In this manner a powerful traction may be produced between the drivingmotor and driven cables where a relatively light car and counterbalanceare used. The suspended beam 12 may be of any desired length.

and arranged to travel in the hatchway upon suitable guides.

Although in the examples given the weight of the two counterweights Wand W taken together is equal to the weight of the car, so that thesystem is balanced when the car is empty, it will be understood thatthis ratio need not be maintained and that in practice the car isusually overbalanced so that an average load on the car is required tobalance the counterweights.

If desired, the auxiliary weight W may be dispensed with entirely andthe same re sults obtained by a readjustment of the other parts. Toillustrate this, let it be assumed that the weight of the parts andtheir arrangement is the same as in the example first given, and the 500pound counterweight IV removed and 500 lbs. added to the counterweightWV. This will not disturb the equilibrium of the system, as the Weight Wwill then balance the empty car. But the tension on the hoisting cableswill be reduced. The tension on the cable 11 at the point 13 is nowsimply that due to the weight of the car acting about the point 18 as afulcrum, that is, 4,000 lbs. To increase this tension to 5,000 lbs. asin the first example, the fulcrum point 18 is moved nearer to the point13, so that the ratio between the two lever arms 13, 18 and 18, 23 is 2to 5. The tension on the cable 11. at the point 13 is then 5,000 lbs;the tension on the cable 14 is 5,000 lbs. plus the weight of the car, or7,000 lbs; the tension on the cable 11 below the counterweight W is7,000 lbs. less the weight W, or 5,000 lbs. It is thus seen that abalance is maintained and the same tension on the hoisting cableobtained without the auxiliary weight W, by a proper adjustment ofparts. The auxiliary weight W, however, forms a ready means foradjusting the tension on the hoisting cables. The tension on the leadsextending from both sides of the driving sheave can be increased ordecreased by adding to or taking from the weight W. By making thedistance between the points 18 and :21 great as compared with thedistance between the points 13 and 18, a wide variation in the tensionof the hoisting cables may be obtained by a small increase or decreasein the weight W. It will also be observed that by transferring a portionof the auxiliary weight WV to the main counterweight W, or vice versa,the tenison on the hoisting cables may be adjusted without disturbingthe balance of the system in the least.

While the foregoing examples are theoretically correct, it should beunderstood that they are given merely as illustrations, as there arevarious conditions met with in practice which would modify the resultsto a certain extent. Such conditions are fully recognized by thoseskilled in the art, and due allowance could readily be made there- WhileI have shown an operative embodiment of my invention, I desire not to belimited to the precise construction and arrangement of parts as hereinshown, since various modifications are possible without departing fromthe spirit and scope of my invention.

What I claim as new and desire to have protected by Letters Patent ofthe United States is 1. In an elevator, the combination with a motor, ofa car, a hoisting cable, a counterweight, a lever forming a connectionbe tween the car and counterweight, and a weight connected to the leverto increase the tension on the hoisting cable.

2. In an elevator, the combination with a motor, of a car, a hoistingcable, a lever connected to the car and cable, and a device connected tosaid lever for increasing the tension on the hoisting cable.

3. In an elevator, the combination with a motor, of a car, a hoistingcable, a beam from which the car is suspended, connections between thecable and beam for supporting the beam and car and placing a tension onthe cable proportional to the weight of the car, and a weight. havingconnections with the beam for increasing the tension on the hoistingcable and also partially counterbalancing the weight of the car.

4. In an elevator, the combination with a motor, of a car, a hoistingcable, connections between the car and cable, and a weight associatedwith said parts, movable at the same speed as the car and increasing thetension on the hoisting cable an amount greater than said weight.

5. In an elevator, the combination with a motor, of a horizontal beam, acable connected at its ends to intermediate points on the beam, a carsuspended from one end of the beam, and a counterweight connected to theother end of the beam and exerting an upward tension thereon.

6. The combination with a driving member, of a load carrying device, ahoisting cable, a device forming aconnection between said load carryingdevice and said cable and operable to maintain tension on the cable, anda weight connected to said connecting device and operable to increasethe tension on the cable.

In testimony whereof, I have signed my name to this specification in thepresence of two subscribing witnesses.

DAVID L. LINDQUIST.

Witnesses CHAS. M. NISSEN, JAMES D. IvERs.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents, Washington, I). 0.

